Refining the indications for neoadjuvant chemotherapy for patients with HER2+ breast cancer: A single institution experience.

Background We aim to compare the clinical outcomes of patients with early-stage HER2+ breast cancer treated with adjuvant chemotherapy (AC) and neoadjuvant chemotherapy (NAC). Methods Patients with non-metastatic HER2+ breast cancer treated from 2009 to 2018 at our institution comprised our study cohort (n = 1254). Pathologic complete response (pCR) was defined as the absence of invasive disease in the breast and axilla after NAC. Log-rank, Kaplan-Meier, and inverse probability of treatment weighting were used to assess differences in disease-free and overall survival between groups stratified by AC vs. NAC and pCR vs. non-pCR. Results The majority received AC (n = 787 or 62.8%) while 467 (37.2%) patients received NAC. Median follow up for AC and NAC groups was 46 and 28 months, respectively. The crude disease-free survival and overall survival of our study cohort were 92.2% and 89.1% for AC, 89.1% and 82.2% for NAC pCR, and 68.1% and 60.0% for NAC non-pCR, respectively. For clinical stage >= IIB patients, NAC conferred a positive but statistically nonsignificant treatment effect over AC in multivariate analysis. Conclusions After adjusting for imbalances in our subgroups, we found that, regardless of the sequence of chemotherapy (AC vs. NAC), patients with early-stage HER2+ breast cancer had excellent outcomes.